1. Field of the Invention
The invention relates to a foldable frame, more particularly to a foldable ladder or chair that is safe to manipulate and use.
2. Description of the Related Art
As working and living spaces become more and more limited nowadays, household items tend to be collapsible or movable so as to occupy less space.
With reference to FIGS. 1 and 2, a conventional foldable frame 10, such as a foldable ladder or chair, is shown to include a pair of upright supporting rods 11, a pair of prop members 12 pivotally connected to the supporting rods 11, at least one crosspiece 13 having one side pivotally mounted on the upright supporting rods 11, a crossbar 14 disposed near a top section of the prop members 12, at least one link 15 connected to the other side of each crosspiece 13, and a retaining link 16 provided on a bottom face of an uppermost one of the crosspieces 13 to be coupled pivotally with the crossbar 14 in a linking-up relationship. Due to the above-mentioned linkage structure, by moving a rear side of the uppermost crosspiece 13, the prop members 12 are caused to move towards or away from the upright supporting rods 11. At this time, the other crosspieces 13 are caused to turn simultaneously to allow the opening or closing of the frame 10. However, although the frame 10 is easy to stow, it suffers from the following drawbacks in use:
Since the linking-up movement of the upright supporting rods 11, the prop members 12, and the crosspieces 13 is achieved by means of the pivotal connections or the links 15 and the retaining link 16, movement of any one of the crosspieces 13 will bring the other structural elements to move therewith. Although a construction as such affords convenience in terms of opening and closing of the frame 10, as the crosspieces 13 have only one side pivotally connected to the upright supporting rods 11 and are without any means to position the same, if the distribution of weight on any one of the crosspieces 13 is concentrated at the pivoted side, or if any one of the crosspieces 13 was bumped into inadvertently, all of the crosspieces 13 will henceforth turn, thereby resulting in abrupt folding of the frame 10, which may cause danger to the user or anyone nearby.